We report calculations of the minimum energy pathways connecting CH2 N2 to diazomethane and diazirine, for the rearrangement of diazirine to diazomethane, for the dissociation of diazirine to HCN2H, and of diazomethane to CH2NN. The calculations use Complete Active Space Self-Consistent Field (CASSCF) derivative methods to characterize the stationary points and Internally Contracted Configuration Interaction (ICCI) to determine the energetics. The calculations suggest a potential new source of prompt NO from the reaction CH2 with N2 to give diazirine, and subsequent reaction of diazirine with hydrogen abstracters to form doublet HCN2, which leads to HCNN(S-4) on the previously studied CHN2 surface. The calculations also predict accurate 0 K heats of formation of 77.7 kcal/mol and 68.0 kcal/mol for diazirine and diazomethane, respectively.